High capacity choke for d.c. installations



Aug. 25, 1959 B. STORSAND HIGH CAPACITY CHOKE FOR D.C. INSTALLATIONS Filed Feb. 28, 1957 IMVN,TORI BEER IVE-15 7 v United rates Patent HIGH CAPACITY CHOKE FOR D.C. INSTALLATIONS Bjarne Storsand, Zurich, Switzerland, assignor to Octlikon Engineering Company, Zurich, Switzerland, a corporation of Switzerland Application February 28, 1957, Serial No. 643,081

Claims priority, application Switzerland March 6, 1956 2 Claims. (Cl. 336-223) This invention relates to a choke of high current-carrying capacity especially adapted for D.C. installations.

The present invention is characterised in that the coil consists of a plurality of consecutive, axially adjacent turns, separated by intervening insulating layers, of an edgewise-wound fiat conductor pierced by holes through which the tie-bolts are passed.

By compressing the turns of a fiat conductor by means of tie-bolts which pass through the actual material of the conductor, a rigid hollow cylindrical coil of exceptionally high mechanical strength is produced, a factor of great importance in high-capacity chokes which are subject to considerable mechanical loads in D.C. installations Where they are used to equalise and smooth the current and to limit the rise in the current when a shortcircuit occurs. These loads are due, on the one hand, to the very high short-circuit-ing currents that sometimes arise and, on the other hand, to the continuously pulsating magnetic forces set up by harmonics.

In a choke constructed in accordance with the invention, the width of the flat conductor, which may consist for instance of aluminum or an aluminum alloy, is prefreably /5 to ,5 of the internal diameter of the coil. The conductor may have such a width because in direct current, the loss due to harmonics is negligible. For a coil with an internal diameter of say 1 metre, for instance a flat material cms. in width can be used, that is to say a material having a width equal to one tenth of the internal diameter of the coil, whereas its thickness may be between 10 and 20 mm.

A choke constructed in accordance with the invention is also intended to suppress the current surge arising in the case of short-circuits. A further advantage of the invention, apart from its mechanical strength, is the fact that when short circuits occur, the D.C. resistance will rise, due to the skin elfect, to several times its normal value, a factor which increases the damping efiect on the surge.

It is preferred in a choke according to the invention to drill holes through the conductor centrally with re- 2,901,717.- Patented Aug. 25, 1959 ICC spect to its width. Tie-bolts of ordinary steel can then be used since the field intensity in the centre of the conductor is small by comparison with that of the principal field.

In order to enable the invention to be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example one embodiment thereof in the form of a high capacity choke, and in which:

Fig. 1 is a side elevational view of a choke of an embodiment of the invention constructed in accordance with the concepts of the invention; and

Fig. 2 a longitudinal sectional view of an embodiment of the invention.

The coil is formed from a flat, edgewise-wound, aluminum conductor 1 of which the ends 2 and 3 are joined to terminals not specially shown. Equidistantly distrib: uted around the circumference of the coil are holes 4 drilled through the centre of the conductor and tie-bolts 6, enclosed in insulating bushings 5, are passed through the holes. The individual turns of the conductor 1 are separated by insulating rings 7 and they are then compressed by nuts 12 through insulating discs 8, compression plates 9, compression springs 10, compression discs 11.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. A choke of high current-carrying capacity coil for direct current installations; comprising a coil formed of an edgewise-wound flat conductor and including a plurality of integrally formed consecutive, axially adjacent coil sections, separated by intervening insulating layers, said sections and said insulating layers having aligned apertures therethrough, a plurality of tie-bolts having insulating bushings thereabout extending through said apertures, compression plates disposed in alignment with said apertures, said compression plates having recesses therein, said tie-bolts extending through said compression plates, nuts threadedly engaged on said tiebolts, and compression springs disposed about said tiebolts seating in said recesses and engaging said nuts.

2. A choke as set forth in claim 1, in which the width of the flat conductor is /s to A of the internal diameter of the coil, said conductor being of aluminum.

Murgas Apr. 2, 1907 Fuglll et al Nov. 21, 1939 

